Cherry pick upstream patch for integer overflow

Fix: https://github.com/unicode-org/icu/pull/253

Bug: https://unicode-org.atlassian.net/browse/ICU-20246

TBR=ftang@chromium.org
Bug: 900059
Test: See the bug
Change-Id: I6c75502e44b41f7b77f6f6265dfd099e42196178
Reviewed-on: https://chromium-review.googlesource.com/c/1312653


Reviewed-by: Jungshik Shin <jshin@chromium.org>